Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$129.62	11.854%	$144.9852	$144.99	$145.00	$145.00
Purchase #2	$113.74	11.227%	$126.5096	$126.51	$126.50	$126.50
Purchase #3	$23.87	5.466%	$25.1747	$25.17	$25.15	$25.20
Purchase #4	$37.46	13.192%	$42.4017	$42.40	$42.40	$42.40
Purchase #5	$143.52	6.434%	$152.7541	$152.75	$152.75	$152.80
Purchase #6	$122.52	4.424%	$127.9403	$127.94	$127.95	$127.90
Purchase #7	$29.76	12.816%	$33.574	$33.57	$33.55	$33.60
7 purchase totals =	$600.49		$653.3396	$653.33	$653.30	$653.40